Salicylic acid minimizes nickel and/or salinity-induced toxicity in Indian mustard (Brassica juncea) through an improved antioxidant system

Introduction This study was hypothesized that salicylic acid elevates the level of antioxidant system that will protect plants from the stress generated by nickel and/or salinity. Materials and methods Seeds of Brassica juncea were sown in sand amended with NiCl₂ (100 mg kg^-1) and/or 15-day-old seedlings supplied for 3 days with NaCl (150 mM) and were then, at 20-day stage, sprayed with salicylic acid (10^-5 M) to assess selected morphological, physiological, and biochemical parameters at 30-day stage. Results The combination of Ni and NaCl proved most deleterious and exhibited significant decline in growth, leaf water potential, the level of pigments, and photosynthetic attributes. However, the follow-up treatment with salicylic acid detoxified the stress-generated damages caused by the combination (NiCl₂ and NaCl) and also significantly improved values for the above parameters. The NiCl₂ and/or NaCl increased electrolyte leakage, lipid peroxidation, and H₂O₂ content but decreased the membrane stability index and activity of nitrate reductase and carbonic anhydrase. However, the salicylic acid treatment in the presence or absence of the stress improved the activity of nitrate reductase and carbonic anhydrase. The activity of antioxidative enzymes and the level of proline exhibited a significant increase in response to NiCl₂ and/or NaCl stress and which enhanced further with the spray of salicylic acid. Conclusions It is concluded that the elevated level of antioxidative enzymes and level of proline might be responsible for minimizing the Ni and/or salinity-induced toxicity in Indian mustard which is manifested in terms of improved growth and photosynthesis.